E. coli membranes are extracted first with 0.4% deoxycholate (DOC) and then with 2% DOC to yield crude perparations of succinate dehydrogenase and cytochrome oxidase. These fractions, when passed together through Sephadex G-75 to remove DOC, regain succinoxidase activity and a particulate structure. When the fractions are individually passed through Sepharose 4B or Bio Gel A 0.1M they lose a significant fraction of their reconstitutive ability. A soluble fraction has been isolated which can restore the reconstitutive ability of the column chromatographed fractions. The soluble factor is heat stable, is not succinate dehydrogenase or cytochrome oxidase, is not Fe55 labeled but does appear to contain phospholipid.